A hybrid vehicle refers to a type of environmentally-friendly vehicle that is driven by efficiently combining two or more types of different power sources, and in general, refers to a vehicle that is driven by an engine for combusting fuel (e.g., fossil fuel such as gasoline) to obtain rotatory power and an electric motor for obtaining rotatory power using battery power.
An engine generates rotatory power by combustion pressure during cylinder explosion stroke. In particular, engine torque contains a vibration component proportional to a number of cylinder explosions per axis rotation due to change in combustion pressure. The vibration component is transmitted to a vehicle body via an engine mount and a drive shaft to cause vibration and noise, thereby causing uncomfortable ride to a driver.
A method (a first method) of changing an engine operating point to avoid a vibration generating range a method (a second method) of reducing vibration using low stiffness of a torsional damper, and a method (a third method) of changing a resonance region by installing a dynamic damper have been developed. However, in the first method an optimum operating point is deviated from, in the second method a low vibration decreases effect due to restriction of low stiffness, and in the third method fuel consumption is degraded due to weight increase and manufacturing costs are increased due to generation of additional expenses.